Author Topic: Silver solder to join aluminum? (Read 31808 times)

Larry Cunningham · « **on:** January 07, 2012, 07:35:32 AM »

I was just watching an episode of "Factory Made" wherein they were showing how bass drums are made. Interesting stuff, one thing caught my eye - they folded a 1" wide strip of aluminum into a U-cross section and rolled that into 22" diameter hoops which attach the drum head. They applied a small dab of silver solder paste to the hoop ends and heated it with a gas flame to join them.

I didn't realize that silver solder would join aluminum parts..

I'll bet someone knows all about this. Comments?

Thanks,

L.

Q. It is considered in bad taste to discuss two subjects at nudist camps. One is politics, what is the other?
A. Paul Lynde: Tape measures. -Hollywood Squares

David M Johnson · « **Reply #1 on:** January 07, 2012, 08:20:22 AM »

I don't know about silver solder but I do know there is a material that harbor freight carries that can be used for castings and sheet aluminum that melts like solder.
David Johnson

John Stiles · « **Reply #2 on:** January 07, 2012, 08:49:41 AM »

Quote from: David M Johnson on January 07, 2012, 08:20:22 AM

I don't know about silver solder but I do know there is a material that harbor freight carries that can be used for castings and sheet aluminum that melts like solder.
David Johnson

Yep, I use it...trick is to heat the metal and brush away the oxidation...then heat the metal but not the solder....rub the solder on the metal till it melts....works on different metals, not just aluminum.

John Stiles · « **Reply #3 on:** January 07, 2012, 08:53:34 AM »

Watch this short clip:

Tim Wescott · « **Reply #4 on:** January 07, 2012, 09:36:41 AM »

Certainly not all, but maybe a little. (All theoretical, and therefore nearly useless).

Regular old silver solder, with regular old flux, doesn't work on aluminum. There are solders that do work on aluminum when paired with really aggressive fluxes, but the ones that I've heard about to date all require you to apply the flux and solder, then scrub the aluminum with something (the one that I have tells you to use a stainless wire brush), then once everything is tinned go ahead and join the parts.

The reason being that aluminum oxide is pretty hard stuff (when you get it in big chunks it's called 'corundum', and you make sandpaper out of it). So the flux needs to both attack the aluminum oxide and protect the surface from the air once the oxide's scraped away, then still allow the solder to get to the surface.

Are you sure the metal being joined was aluminum and not tinned steel?

john e. holliday · « **Reply #5 on:** January 07, 2012, 09:41:44 AM »

The short video of the sealing of a hole in the bottom of a coke can was interesting. Wonder if the "Durafix" would work on our small engines. Looks like the drill had to work a little to get thru the stuff.

Tim Wescott · « **Reply #6 on:** January 07, 2012, 10:04:40 AM »

Quote from: john e. holliday on January 07, 2012, 09:41:44 AM

The short video of the sealing of a hole in the bottom of a coke can was interesting. Wonder if the "Durafix" would work on our small engines. Looks like the drill had to work a little to get thru the stuff.

I don't know. I got an aluminum soldering kit from my local welding shop which I haven't used. The solder is mostly zinc; the MSDS on the flux is dire enough that I'd want to have a fan running, or do it on the porch on a breezy day.

Brett Buck · « **Reply #7 on:** January 07, 2012, 12:06:19 PM »

Quote from: John Stiles on January 07, 2012, 08:49:41 AM

Yep, I use it...trick is to heat the metal and brush away the oxidation...then heat the metal but not the solder....rub the solder on the metal till it melts....works on different metals, not just aluminum.

Yes, I got some of that welding rod. They were selling (and doing this demonstration) at the 96 NATs. It's eutectic welding rod and needs no flux. I practiced for a while and got to the point that it was easy to bridge gaps, etc, with it (not Coke cans, Diet Squirt - the Pink Refresher!) and it was as easy as it seemed. When I tried to make up parts with it, I found it much harder to do. It doesn't work much like solder, that's for sure. I ended up making an aluminum tank with it but I was never satisfied with the results and the weight of the weld material ended up making the tank a lot heavier than a regular tin-plated-steel tank.

In my case it's very possibly a matter of technique that I just never mastered. If you have any ideas on how to use it to make parts (tanks, brackets, etc) I would appreciate some pointers.

Brett

John Stiles · « **Reply #8 on:** January 07, 2012, 12:52:37 PM »

Quote from: Brett Buck on January 07, 2012, 12:06:19 PM

In my case it's very possibly a matter of technique that I just never mastered. If you have any ideas on how to use it to make parts (tanks, brackets, etc) I would appreciate some pointers.

Brett

Naw, I never tried to cast parts or build tanks....I use it some on my mufflers....patch boats...even repaired a broken handlebar on my husqvarna, and a broken boat prop! The stuff is harder than aluminum, and heavier. Perfect for repairs though.

Brett Buck · « **Reply #9 on:** January 07, 2012, 01:03:11 PM »

Quote from: John Stiles on January 07, 2012, 12:52:37 PM

Naw, I never tried to cast parts or build tanks....I use it some on my mufflers....patch boats...even repaired a broken handlebar on my husqvarna, and a broken boat prop! The stuff is harder than aluminum, and heavier. Perfect for repairs though.

That's about what I found - if the goal was to patch holes in aluminum, it works almost miraculously well. But it was not that easy to actually build stuff with it. It's really hard, and sticks very well, but it doesn't want to flow into joints like solder, just sort of sits on the surface in globs.

Brett

Dallas Hanna · « **Reply #10 on:** January 07, 2012, 01:50:03 PM »

This was one type being marketed at shows in the UK.

!

Works well on aluminium muffler fabrication. The muffler below was only joined at the inlet tube and end plate. Pop rivets were used to hold both end components into the tube so that changes could be made if required. Front end plate and tail cone is light interference fit in tube.

HH

Lauri Malila · « **Reply #11 on:** January 07, 2012, 01:53:59 PM »

Hi.

There are 3 main problems in aluminium brazing:

-Getting rid of the oxide. (Well, I don't really see it as a problem as it can be taken care of with the flux that comes with the solder/braze. The flux can be in the solder bars, or it can be a separate paste that is applied to the surfaces before applying the solder.) ((In my opinion, if the flux is within the solder bars like in those "Miracle" products, you cannot expect a good diffusion of the braze into the workpiece.))

-The melting temperature of aluminium is usually VERY close to the melting temperature of the solder/braze material, and aluminium does not give much signs of it's temperature (colour change, glow) before it suddenly melts. This together with the fact that aluminium conducts heat very well, and because of small density, does not keep the temperature very well, makes it difficult to braze especially larger parts. Also, as you cannot estimate the correct temperature from the metal, the behaviour of flux can give good indication.
The correct way is to heat the complete parts that are being joined joined very close to the final temperature, and when the braze starts showing signs of melting, to quicly add heat to the place where you want the braze to flow. The braze allways flows towards the hottest place.

-As aluminium conducts heat so well, it is important to hold the workpiece so that heat cannot conduct away. So, don't hold it in a vice for example. I usually rely on good fits, meaning that the parts to be joined stay together without any solder. You can also wrap the parts together lightly with thin mild steel wire (from flower shop). Also, all kinds of pieces of ceramic tiles can be used to support the workpiece.

I have tested many of the "Miracle" solders & brazes that they sell at all kinds of modelling exhibitions and trade shows and found them mostly crap. They can be OK in places were high strenght is not important. With them it is also possible to join alloys that are impossible or at very difficult to join with better products.

Also, making "bridges" and "building up" material a lot is not possible with a good braze, like with Castolin Eutectic's 190. It really flows well and goes into gaps with capillary action. The same 190 can also be TIG welded and maybe building up material is possible with that method, I don't know.

I think that the Castolin 190 or similar could be used in making aluminium fuel tanks, but heating the seams can be tricky.

I hope this makes sense.

Lauri

John Fitzgerald · « **Reply #12 on:** January 07, 2012, 03:26:56 PM »

http://www.acehardware.com/product/index.jsp?productId=1290590

I tried this stuff. Had to use Mapp gas to get hot enough. Joints were very brittle. Ended up taking the piece to a pro; he tig welded it in ten minutes; cost me $15; worth it.

George · « **Reply #13 on:** January 08, 2012, 01:21:24 AM »

The brand I have is called ALUMIWELD and yes, there is a learning curve. If you are going to use it, learn first before trying to repair something.

IMHO, for a one time shot get a professional.

George

Andrew Tinsley · « **Reply #14 on:** January 08, 2012, 05:50:05 AM »

The short answer is no! Silver solder does not work on aluminium! The eutectic type material and scratching the surface of the material to be joined, does work. It is largely a matter of technique. Most people give up way too soon and say that it is "No good". It takes some real practice to master the art, but if you do, then the results are excellent. I have repaired broken off mounting lugs and cracked cylinders and they are still in one piece after years of use.
I think it was Ron (F4F guy), that said in an older thread, that repairs made with eutectic alloys were very inferior in strength to the base casting material. He is probably quite right in saying this. However repairs I have made, suggest that the joints are strong enough for purpose.
Is it worth the effort in acquiring the necessary skill ? To be frank it is probably not worth the hours and expense involved. The only real way of welding aluminium is to use TIG welding with the appropriate gas shielding, Oh and you need to get the metal hot (probably 300 degrees plus) for it to work really well.
My father was a sheet metal worker and oxy-acetylene welder. I have seen him weld a broken cast gear box cover, off a M/cycle. He used an aluminium filler rod and straight oxyacetylene. Most people say that this is impossible, however I saw it done. My father said the secret was to get the base material just below melting point and the rod just above melting point. One false move and a large hole resulted! He recalled a time when he demonstrated this to a BOC welding expert who was derisive that my old man could do it! He went away very chastened!
Things have moved on and you can now buy a rod and flux from BOC (and I assume other welding companies) you do need oxyacetylene, people say you can use map gas and oxygen, but I have not tried it. These items work very well but it is quite expensive and I think I am probably one of the very few aeromodelers that has his own oxy-acetylene rig. If I costed the cylinder rental per job, let alone the consumable costs, I must have the most expensive welding shop in the world!

Regards,

Andrew.

John Stiles · « **Reply #15 on:** January 08, 2012, 08:08:30 AM »

Quote from: Andrew Tinsley on January 08, 2012, 05:50:05 AM

I think I am probably one of the very few aeromodelers that has his own oxy-acetylene rig.

Regards,

Andrew.

....I have both oxy-acetylene, and map gas. I own my bottles, and it's still pretty expensive. I sometimes use two or three bottles of oxygen to one bottle of acetylene, depending on how much cutting I do. Also have wire and stick welders....the argon bottle I rent. But on a farm....you either do that or spend yourself broke hauling your stuff to town to get repaired. I tried a M/C transmission case once....the hole got bigger. Wound up fiber-glassing it, which lasted years.

Tim Wescott · « **Reply #16 on:** January 08, 2012, 09:43:30 AM »

Few, maybe, but not only -- I have an oxy-acetylene rig and a wire welder. Both get used far more for car jobs and repairing stuff around the property than for model aviation, but since I have them they get used there, too.

Lauri Malila · « **Reply #17 on:** January 08, 2012, 10:20:23 AM »

Hi again.

I may have misunderstood something, but for the ordinary stuff in aeromodelling, like making and fixing mufflers, pipes, headers and maybe fuel tanks, there is no need for an oxygen bottle system. If you really have to fix broken crankcases and other cast parts, TIG is usually the way to go. But even if I could use TIG, I would never fix broken cases. Some things are just not ment to be repaired.
The only negative thing with the Castolin stuff that I use, is that as I must heat the whole workpiece, it looses some strenght (softens). I would be very interested to hear if it would be possible to gain back the original strenght with a heat treatment.

L

Tim Wescott · « **Reply #18 on:** January 08, 2012, 11:12:35 AM »

Google "Aluminum heat treat", or perhaps "Aluminum precipitation harden". Or let someone do it for you: http://en.wikipedia.org/wiki/Precipitation_hardening.

To my knowledge, most non-ferrous metals heat treat the reverse of steel: to soften them, you heat them up slow and quench them fast, while to harden them (if they can be hardened at all) you hold them at a moderate to high heat for a long time, then let them cool slowly. Particularly with aluminum I'm pretty sure that if it's hardenable at all, the way to do it is with precipitation hardening or just plain aging.

Mark Scarborough · « **Reply #19 on:** January 08, 2012, 11:24:50 AM »

Tim as you say, heat treating aluminum is kinda tricky.
from what I recall of my time in the aero repair industry , fixing broke crop dusters,,
different alloys require different methods,, some radically so.
I cant recall which alloy it was, but it would harden with age, so you would anneal it, work it, then just let it sit around for a period of time and magically

it would go back to the harness you desired,,
others ,, ( my memory says 5051 but that could be wrong) we would get it in an "0" state, and it was used for holding windscreens in place and things like that, it was wonderfully mallable, dead soft,, it was like working with a peice of leather or something it was that workable,,but if you looked at the strenght, not so much,,

To weld or work a crankcase of aluminum, I would think it extremely critical to know what alloy was used, otherwise you could process it wrong and destroy it,,
as was mentioned in another post, some things are meant to be replaced not repaired,,

Tim Wescott · « **Reply #20 on:** January 08, 2012, 11:35:20 AM »

Quote from: Mark Scarborough on January 08, 2012, 11:24:50 AM

To weld or work a crankcase of aluminum, I would think it extremely critical to know what alloy was used, otherwise you could process it wrong and destroy it,,
as was mentioned in another post, some things are meant to be replaced not repaired,,

I would approach a crankcase repair with the attitude that either (a) the engine is usable, so don't mess with it, or (b) the crankcase is already a throwaway, so why not give it a whirl?

Aluminum has to be alloyed to harden: 3003 aluminum is soft, and 1100 aluminum is even softer; neither will ever get hard with age or any other treatment (pure iron is softer than aluminum, by the way, but it's fairly hard to get iron without at least some carbon in it, and who would want it?).

Dallas Hanna · « **Reply #21 on:** January 08, 2012, 02:20:58 PM »

The stuff at the British Nats, 2011 was Alutight. The demo was in my previous post. The instructions specify "do not use acetylene gas". Not sure on the chemistry reason but the oxy/acet flame is much hotter than butane and it is harder to control the heat on small sections. Butane worked great on my muffler fabrication use. The material is only 0.6mm thick.

Alutight wasn't cheap but I did get near 2 metres for 25 Quid at the Britis Nats last year. It certainly worked better than the Lumiweld which is zinc based, but mainly I think by only having to scratch through the oxide layer rather than the wire brushing/tinning process required in the use of Lumiweld.

Instruction sheets attached. If there's any wrong info on the sheets please contact the supplier!!

HH

proparc · « **Reply #22 on:** January 08, 2012, 09:38:08 PM »

I tig weld. Make sure rig is set to AC. It blasts the oxides away that form to get your weld. That's what that noise is when your welding. Tig welding aluminum is very difficult. Beryllium is even tougher still!!

Andrew Tinsley · « **Reply #23 on:** January 09, 2012, 01:15:37 PM »

For some reason a previous reply didn't make it to the forum. Probably due to poor finger co ordination.
I would not dream of trying the eutectic type rod with oxy acetylene, the temperatures required for the process are very low, use a butane torch if you want to try it!
Frankly, I don't consider it worth while to learn the technique, it took me a lot of time to become proficient and for the odd repair, it just isn't worthwhile! Mind you, it does work if you can be bothered to gain the experience.
I would use Tig welding for any future repair, but you do need to get the workpiece hot before it works really well (maybe it was the filler rod I used?)The story of my old man welding aluminium castings with oxy-acetylene and filler rod was just to illustrate what you can do if you are a real craftsman. There is no way I could do it. my father died a few years ago at the age of 96, so it is a bit late for me to get any tuition

Regards,

Andrew.

Phil Coopy · « **Reply #24 on:** January 09, 2012, 04:57:30 PM »

I a hobbyist welder. I've built lots of custom aluminum mufflers and used both TIG and eutectic rod on them. I prefer to use Aladdin Rod on mufflers because of the thin sheet I use for them. With a TIG it is easy to blow a hole in thin materials and then you end up with a messy looking job after you fix it. It just takes practice with the zinc(eutectic) filler rods. I have never used oxy/acetylene on aluminum..I always figured it would be too hard to achieve a non oxidizing flame balance especially as fast a aluminum likes to oxidize. I have never used silver solder with aluminum but do use it with stainless.

Advice to those of you who dream of having a TIG welder for hobby use................when word gets around, the line up of broken golf carts, cracked crank cases, lawn chairs, alloy rims, and other neighborhood aluminum repair "favors" waiting at your shop door will never end.

Phil

Andrew Tinsley · « **Reply #25 on:** January 10, 2012, 06:39:33 AM »

Phil is absolutely correct! Don't let people know you can fix it, otherwise you will drowned with "little jobs". I got a top of the range Tig welder out of the skip when my old company closed down a section. I really thought I had done well with the TIG welder (legally acquired by the way!). Now I am not too sure...................exactly what Phil said!

Andrew.

john e. holliday · « **Reply #26 on:** January 10, 2012, 08:07:56 AM »

Hang a labor charge on the favors and they will disappear.

It is amazing how many friends you have when they find out that you equipment to do things.

John Fitzgerald · « **Reply #27 on:** January 10, 2012, 08:36:03 PM »

Quote from: john e. holliday on January 10, 2012, 08:07:56 AM

Hang a labor charge on the favors and they will disappear. It is amazing how many friends you have when they find out that you equipment to do things.

How true.

Clayton Berry · « **Reply #28 on:** January 12, 2012, 10:42:24 AM »

Sort of like owning a pickup truck. Amazing how much furniture your mother-in-law can go thru over the years.

And the difference between an in-law and and an outlaw? An outlaw is at least wanted by someone.

And always remember - a friend will help you move. A good friend will help you move a body.

Joseph Lijoi · « **Reply #29 on:** January 12, 2012, 01:10:55 PM »

Larry,

What started this thread was the drums. I have a drum set here and play the drums. Drum hoops are wood, cast steel or stamped steel for acoustical reasons. A bass drum hoop is wood. I think what they were explaining was the hoop for a drum head, which is aluminum. Chances are seam is glued, because the head (mylar) is also glued and crimped to the hoop. The drum head that I have in my hand looks like it is glued, so I really doubt that silver solder is used.